Botulism or botulinus intoxication is a serious and potentially fatal disease in humans and animals. Botulism is usually an intoxication caused by intake of preformed toxin. It may also happen that spores of C. botulinum germinate in the intestine or in a deep wound and the bacteria may then start to produce toxin. This condition is termed a toxicoinfection.

The different toxin types have the same basic structure and mechanism of action, but are serologically distinct. Botulinum toxin is a neurotoxin, which is similar to tetanospasmin in structure and mode of action, but they act on different parts of the nervous system. Botulinum toxin is (like tetanospasmin) composed of two protein subunits and one is a protease that destroys the fusion protein to which vesicles containing acetylcholine should bind. Thereby inhibiting the signal transduction between the efferent (= motoric) nerve and muscle cells by preventing vesicles from anchoring to the membrane to release acetylcholine.

About 180 differens species have been descibed within genus Clostridium. C. botulinum can be classified into four different phenotypic groups: I-IV.C. botulinum-strains within group I are most closely related to Clostridium sporogenes and Clostridium putrificum and not to any of the other three phenotypic groups of C. botulinum.

In Sweden, botulism in animals and humans is notifiable to the Swedish Board of Agriculture and the Public Health Agency of Sweden, respectively. Clostridium botulinum belongs to category A as a potential bioterrorism agent according to NIAID.

Clostridium botulinum actually represents four different species (phenotypic groups), all of which have at least one of the botulinum toxin genes. The type strain is of toxin type A. In the case of C. botulinum, you can really say that taxonomy is not consistent with phylogeny.